The present invention pertains generally to lasers and more particularly to freguency control of diode lasers.
A major disadvantage of the diode laser has been the inability to achieve good mode control within the diode lasing medium. Various distributed feedback systems have been used in the prior art to alter the reflectivity of the medium in a periodic fashion to achieve good mode control. Typically semiconductor lasers, such as diode lasers, are mechanically etched or ruled in a direction perpendicular to the lasing axis. This procedure is time consuming and expensive, and generally constitutes a poor manner of achieving mode control. Moreover, the mode of operation of the diode laser is fixed once this technique of mechanical etching or ruling has been performed.
Another disadvantage of the diode laser has been its relatively low output powers. Typically, DC currents are utilized to pump the diode laser to initiate lasing. Alternatively, optical pumping of semiconducting diode lasers has been performed such as disclosed in IEEE Journal of Quantum Electronics, 9, 347 (1973). However, no method has been disclosed for varying the reflectivity of a diode medium in a periodic fashion to vary the output frequency.